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• • 




LONE STAR CEMENT CORPORATION 

MAKERS OF LONE STAR CEMENT . . . 'INCOR' 24-HOUR CEMENT 

General Offices. 342 MADISON AVENUE. NEU YORK. Sales Offices: ALBANY, BIRMINGHAM, BOSTON. CHICAGO. DALLAS. HOUSTON. 
INDIANAPOLIS, KANSAS CITY. NEW ORLEANS. NEW YORK. NORFOLK, PHILADELPHIA. ST. LOUIS. WASHINGTON. D. C. 



Copyright, Lone Star Cement Coloration, 1938 

All rights reserved 






■ • 






)o13-l% 




9 



1 




uilding jobs which are rushed to completion 
have one thing in common with jobs where there is no pressure for 
fast work — in both cases, lowest construction costs result from 
the best use of time . . . How time affects frame erection costs, and 
how savings can readily be estimated in advance, is told in the 
following pages. These principles apply not only to buildings but to 
all structures on which there is an opportunity to re-use forms. 



> • 



% 






3 

3 



• 



• • 




Popham Hall Apartments, Scarsdale, N. Y. 



Here are two buildings, one a concrete skeleton frame apartment 
house (above), the other a steel-frame office building (at right). 
On one, the contractor was working against time— the apartment 
house had to be ready for early occupancy; on the office building, 
there was no pressure for early completion. Yet, on both jobs, 
cost studies showed that substantial net savings were realized, by 
utilizing erection schedules which made the best use of time. The 
rush job showed a net saving of $1.45 per cu. yd. of concrete; on 
the other job, the net saving was $1.49 per cu. yd. of concrete. 



• • 



* • 










T is a generally accepted fact that rush 



have been completed at little or no extra cost. 



work increases building costs, due to over- simply because faster construction schedules 
time, confusion and lost motion. Yet, con- produced savings in frame erection which off- 



tractors' cost sheets show that many rush jobs 




set increased costs in subsequent operations 

A number of questions immediately 
come to mind. 

Why is it that rush jobs frequently 
show savings in frame-erection costs? 
Are similar savings possible on jobs 
where the contractor has no reason 
to push the work? Are these econo- 
mies obtained only on concrete frame 
structures, or on steel-frame and wall- 
bearing jobs as well? How can the 
contractor find out in advance which 
erection schedule will produce the 
lowest concreting cost? 



WHAT COST STUDIES SHOW 



New England Power Company Building, Boston 



Detailed cost studies now make it 
possible to answer these and related 
(juestions. These studies show that 
the frame is the only part of the build- 
ing where time can be saved at no 
extra expense, and often at a sub- 
stantial saving. 

Thus, six recent jobs, analyzed in 
detail with the cooperation of the 
contractors, have shown net savings 
of from 38c to $1.49 a cubic yard of 
concrete, simply because the con- 



3 



tractors used erection schedules which pro- 
duced the lowest overall cost of time, forms 
and cement. 



week to week and month to month. 

This investment can only earn a return while 
actually working; idle time brings no income, 
yet outgo keeps up just the same. Therefore, 
HOW TIME AFFECTS COSTS t | ie more wor k the contractor completes in a 

The reason is clear enough, when you stop to year, the lower the daily time cost charged 

■ ■ « 



think about it: 

Time obviously costs money, because the 



against each job. 

The same principle applies to the individual 



contractor's investment in organization, equip- job; in fact, the difference between profit and 
ment and in his own skill and experience, rep- loss frequently turns on this very point; short- 
nt fixed costs which run on steadily, from ening the time required to complete a job, 



rese 




4 



lowers the cost — provided, of course, that the 
value of the time saved exceeds the cost of 

saving it. 

An analysis of concreting operations dis- 
closes the reasons. 



strong enough to permit removal of 
forms. 

The contractor is paid for work in place, so 
the second or concreting period is the one that 
actually produces income. All other days are 



ERECTION TIME ANALYZED 



consumed getting ready to pour, or in waiting 
for concrete to become service strong, so that 
The time required to concrete a building di- forms can be stripped and re-assembled for the 



vides into three parts: 

(1) days required to assemble forms 
and set steel and conduits; 

(2) days required for placing concrete ; 

(3) time elapsing until concrete is 



Time required to concrete a building frame di- 
vides into three parts: (1) Form assembly; (2) 
placing concrete; (3) waiting for concrete to be- 
come self-supporting. Since the contractor is 
paid for work in place, the second or concrete- 
placing period is the one that actually produces 
income. Days saved in the form-assembly and 
strength -gaining periods shorten the interval 
between pours; hence, more income-producing 
work can be completed in a given time. While 
the first period is more or less fixed by job condi- 
tions, the third or strength-gaining period can 
be long or short, depending upon the quantity 
and type of cement used. 



next cycle of operations. 

If time can be saved in the first and third 
periods, the total amount of income-producing 
work completed in a week or a month can be 
increased. 



STRENGTH-GAINING TIME 
DECIDING COST FACTOR 

The number of days in the first period, getting 
ready to pour, is pretty much fixed by job 
conditions; relatively little time can be saved 
there. But the length of the third or strength- 
gaining period can be increased or decreased, 
depending upon the kind and quantity of ce- 
ment used in the mix. Examples: 

A concrete made with 5 gal. of water per 
bag of cement gains strength faster and per- 
mits form removal sooner than an 8-gal. con- 
crete. 

Also, a concrete made with 'Incor' 24-Hour 
Cement hardens rapidly and permits form re- 
moval after one or two days; while Lone 
Star Cement, which hardens less rapidly, re- 
quires 3 to 7 days for service strengths. 

Then, too, cold concrete hardens slower than 
warm; and concrete kept wet after placing 
gains strength faster than if allowed to dry out. 

So, this third or strength-gaining period can 
be greatly reduced, or in fact eliminated, in 



5 



so far as it affects job progress. 

TWO WAYS TO REDUCE 
TIME BETWEEN POURS 

Time between pours can be minimized, and 
output of income-producing work increased, 
by using a concrete which produces early 
strength. Similar results can be obtained by 
using a second set of forms. Which method 
to use depends upon the value of the 
time saved, as compared with the 

cost of saving it. 

Tables I and II show how different 
strength-gaining periods affect total 



The strength-gaining period's retard- 
ing effect upon job progress can be 
el iminated by using high early strength 
concrete, or a second set of forms. In 
either case, the time between pours is 
minimized and output of income- 
producing work increased. Which 
method to use depends upon the value 
of the time saved, as compared with 
the cost of saving it. This can be de- 
termined by a comparison of the over- 
all cost of time, forms and cement. 



construction time in buildings of 2 to 16 stories. 
Forming schedules of 3 to 6 days per floor are 
shown, with strength-gaining periods of one 
day to two weeks. 

EXAMPLE ILLUSTRATES 
USE OF TABLES III 

If it takes five days to assemble forms, and 
the strength-gaining period is 7 days, total con- 




6 



Table I 



ummary: Working days required ior completion ot eo] 
frame for different forming and curing schedules. 



Days 
Forming 



Days 

Form 

Removal 



5-DAY WEEK 



3 



Workdays Required to Erect Frame of 2 to 16 Floors 



6 



to 



11 



12 



14 



15 



1 SET OF FORMS 



i 

4 
5 
6 

I 

4 
5 

6 

3 

4 
5 
6 

3 

4 
5 
6 

3 

4 
5 

6 

i 

4 
5 

6 

I 

4 
5 
6 

3 
4 
5 
6 



1 
1 
1 
1 

2 
2 
2 
2 

a 

i 

3 

4 
4 
4 
4 

5 
5 
5 
5 

7 
7 

7 
7 

10 
10 
10 
10 

14 
14 
14 
14 



H 


12 


10 | 


15 


12 


18 


1* 


21 


9 


14 


10 


15 


13 


20 


15 


22 


9 


14 


10 


15 


14 


21 


16 


25 







9 


14 


11 


19 


15 


22 


17 


27 


10 


16 


12 


20 


16 


26 


17 


27 


12 


20 


14 


23 


16 


26 


18 


29 


14 


24 


15 


25 


19 


31 


21 


35 


17 


30 


19 


33 


21 


36 


23 


39 



16 
20 

24 
28 

19 
20 

26 
30 

19 
20 

^2 

19 

25 
31 
37 

24 

27 
36 

37 

28 
32 
36 
40 

34 

35 
44 

47 

43 

47 
51 

55 



20 

25 

30 
35 

24 

25 
33 
37 

24 

25 
36 
41 

24 
SI 

40 

47 

30 



46 

47 

36 

41 
46 
51 

44 
45 

56 
61 

56 
61 

66 
71 



24 
30 
36 
42 

29 
30 

40 

45 

29 

H 

44 

50 

29 
39 

47 
57 

36 
42 

56 
57 

44 

50 
56 
62 

54 

55 
69 
75 

69 
75 
81 

87 



28 
35 

42 

49 

34 

35 
46 
52 

34 



51 

57 

34 

45 
56 
67 

44 

50 

66 
67 

52 
59 
66 

73 

64 
65 
81 

87 

82 
89 

96 
103 



32 
40 

48 
56 

39 
40 
53 
60 

39 
40 

59 

66 

39 
51 

65 

77 

50 

57 
76 

77 

60 
68 
76 

84 

74 

75 

94 

101 

95 
103 
HI 
119 



36 

45 
54 
63 

44 

45 
60 
67 

44 
45 

66 

75 

44 

59 

72 
87 

56 
65 
86 

87 

68 

77 
86 
95 

84 

85 

106 

115 

108 
117 
126 
135 



40 
50 
60 
70 

49 
50 
66 

75 

49 

50 
74 
82 

49 
65 
81 
97 

64 

72 
96 
97 

76 

86 

96 

106 

94 

95 

119 

127 

121 

131 
141 
151 



T 



44 

55 
66 

77 

54 



73 
82 

54 
55 
81 
91 

54 

71 

90 

107 

70 

80 

106 

107 

84 

95 

106 

117 

104 
105 
131 
141 

134 
145 

156 

167 



48 
60 
72 
84 

59 
60 
80 
90 

59 

60 

89 

100 

59 

79 

97 
117 

76 

87 

116 

117 

92 
104 
116 
128 

114 
115 
144 
155 

147 
159 

171 
183 



T 



52 
65 
78 
91 

64 
65 
86 

97 

64 

65 

96 

107 

64 

85 
106 
127 

84 

95 

126 

127 

100 
113 
126 
139 

124 
125 
156 
167 

160 

173 
186 
199 



56 
70 
84 
98 

69 

70 

93 

105 

69 

70 

104 

116 

69 

91 

115 

137 

90 
102 
136 
137 

108 
122 
136 
150 

134 

135 
169 
181 

173 
187 
201 
215 



60 

75 

90 

105 

74 

75 

100 

112 

74 

75 

111 

125 

74 

99 

122 

147 

96 
110 
146 

147 

116 
131 
146 
161 

144 
145 

181 
195 

186 
201 
216 
231 



2 SETS OF FORMS 



4 

5 

6 



7 


8 


12 


16 


20 


24 


28 


10 


10 


15 


20 


25 


30 


35 


9 


12 


18 


24 


30 


36 


42 


10 


14 


21 


28 


35 


42 


49 



T^ 



32 
40 

48 
56 



36 

45 
54 
63 



40 


44 


48 


52 


50 


55 


60 


65 


60 


66 


72 


78 


70 


77 


84 


91 



56 
70 
84 
98 



60 

75 

90 

105 



Days 
Forming 



T Kl II Summary: Working days required for completion of concrete 
I ED 16 11 frame for different forming and curing schedules. 

l. r\4 v ii/crif 



Days 

Form 

Removal 



6-DAY WEEK 



Workdays Required to Erect Frame of 2 to 16 Floors 



3 



8 



10 



11 



12 



13 



14 



15 



> 



1 SET OF FORMS 



. 



3 

4 
5 
b 

3 

4 
5 
6 

3 

4 
5 
6 

4 
5 
6 

3 

4 
5 

4 
5 
6 

4 
5 

6 

3 
4 
5 
6 



3 
3 

3 
3 

4 
4 
4 

4 

5 
5 
5 
5 

7 
7 
7 
7 

10 
10 
10 
10 

14 
14 
14 
14 



8 
10 
12 
14 

9 
11 
12 
15 

10 

II 
13 
16 

10 
12 
14 
17 

11 
13 
15 
18 

13 
15 

17 
19 

16 
17 
19 
22 

19 

21 
23 

25 



12 
15 

18 
21 

14 
17 
18 
23 

16 
17 
21 

25 

16 
19 
23 
26 

18 
22 
24 

2H 

22 

25 

>8 

31 

28 

29 

37 



37 
40 
43 



16 

20 
24 

19 

23 
24 
31 

22 

23 

29 
34 

22 
27 
31 
36 

25 
30 
33 

38 

31 

35 
39 
43 

40 
41 

47 
52 

49 

53 
57 
61 



20 

25 
30 
35 

24 

W 

30 
39 

28 
29 

36 
43 

28 
35 
40 

45 

53 

3K 

42 
49 

40 

45 
54 

55 

60 
67 

64 
69 
74 
79 



24 
30 
36 
42 

28 
35 

36 

47 

34 
35 
43 

52 

34 

42 

48 

55 

40 
47 
51 
60 

49 
55 

61 
67 

64 
65 

82 

79 

85 
91 
97 



28 
35 
42 
49 

33 
41 

42 
55 

40 
41 
51 
61 

40 
49 

56 

64 

47 
55 
60 
70 

58 
65 
72 
79 

76 
77 
87 
97 

94 
101 
108 
115 



32 
40 

48 
56 

38 

47 
48 
63 

46 

47 
59 

70 

46 

57 
65 
71 

54 
63 
69 
80 

67 

75 
83 
91 

88 

89 

101 

112 

109 
117 
125 
133 



36 

45 
54 
63 



53 

54 
71 

52 
53 

66 
9 

52 
65 
73 
83 

61 

72 
78 
91 

76 

85 

94 

103 

100 

101 

114 
127 

124 
133 
142 
151 



40 
50 
60 

70 

48 
59 
60 
79 

58 
59 
73 
88 

58 

72 
82 
93 

69 

80 

87 

102 

85 
95 

105 

11 

112 
113 

127 

142 

139 
149 
159 
169 



44 

55 
66 
77 

52 
65 
66 
87 

64 
65 
81 
97 

64 

79 

90 
102 

76 

88 

96 

112 

94 
105 
116 
127 

124 

125 
141 
157 

154 
165 
176 

187 



48 
60 

72 

84 

57 
71 
72 
95 

70 
71 

89 

106 

70 

87 

98 

112 

83 

97 

105 

122 

103 

115 

127 
139 

136 
137 
155 
172 

169 
181 

193 
205 



52 
65 
78 
91 

62 

77 

78 

103 

76 

77 

96 

115 

76 

95 

107 

121 

90 
105 
114 
133 

112 

125 
138 
151 

148 
149 
168 
1H7 

184 
197 

210 
223 



56 
70 

84 
98 

67 

83 

84 

111 

82 

83 

103 

124 

82 
102 

115 
131 

97 
113 
1 
144 

121 

135 
149 
163 

160 
161 
181 
202 

199 

213 
227 
241 



60 

75 

90 

105 

72 

89 

90 

119 

88 

89 

111 

133 

88 
109 
124 
140 

105 

122 
132 
154 

130 
145 
160 
175 

172 
173 
195 
217 

214 

229 
244 
259 



16 



64 

80 

96 

112 

79 

80 

106 

120 

79 

80 

119 

132 

79 
105 
131 

157 

104 
117 
156 

157 

124 

140 
156 

172 

154 
155 
194 

207 

199 
215 
231 

247 



64 

80 

96 

112 



16 



64 

80 

96 

112 

76 
95 

96 

127 

94 

95 

119 

142 

94 
117 
132 
150 

112 
130 
141 
164 

139 
155 

171 
187 

184 
185 
209 
232 

229 

245 

261 

:*7 



2 SETS OF FORMS 




3 

4 
5 
6 



6 

9 
9 



8 


12 


16 


20 


10 


IS 


20 


25 


12 


18 


24 


30 


14 


21 


28 


35 



24 

30 
36 
42 



28 

35 
42 
49 



32 
40 
48 
56 



36 



^4 

63 



40 
50 
60 
70 



44 

55 
66 

77 



48 

no 
72 
84 



52 
65 
78 
91 



. 



•>6 


60 


64 


70 


75 


19 


84 


90 


96 


98 


105 


112 



7 



struction time for 8 floors, working five days 
per week, will be 76 days. 

With the same 5-day forming schedule but 
with a one-day strength-gaining period, the 76 
days is reduced to 48, saving 28 days. The 
same number of days can be saved, in this in- 
stance, by using 9-day concrete with an extra 

set of forms. 

Then come these questions: 
How much is 28 days worth r What 
will it cost to save that much time? 
Which is cheaper, early strength con- 
crete, or an extra form set ? Answers 
are readily obtained by comparing 



the overall cost of Time, Forms and Cement. 

COMPARE OVERALL COST OF 
TIME, FORMS AND CEMENT 

Substantial savings are often realized by ap- 
proaching each job from this standpoint, so 
let us consider each of these cost items in turn. 

1. TIME COSTS: 

Time costs, often under-estimated in figur- 



Time Costs, often under-estimated 
in figuring a job, are made up of gen- 
eral overhead, job overhead and equip- 
ment charges. These costs, which the 
contractor pays whether he figures 
them or not, usually exceed $50 a day 
even on small jobs, and range from 
$100 to $200 a day on jobs of moder- 
ate size. They are called Time Costs 
because the total of these fixed daily 
charges depends upon the time it 
takes to finish a given job; the longer 
the time, the higher the total Time 
Cost or overhead. 




8 



ing a job, are so called, because the total of the contractor's own time, plus general office 
these cost items charged against each job de- expense— rent, light, heat, salaries, etc. These 



pends upon the time it takes to finish that 
job; the longer the time, the higher the Time 
Cost or overhead. Time costs are made up of: 
(a) General Overhead, (b) Job Overhead, and 
c) Equipment Charges. 

(a) GENERAL OVERHEAD: 



charges, without counting taxes and insurance, 
amount to at least 325 a day, and may run 
from 350 to 3100 a day or more. 

General Overhead runs on from week to 
week and month to month; the sooner a job is 
completed, the lower the proportion of general 



General Overhead includes the value of overhead charged against it, and the greater 

the opportunity to increase the an- 
nual volume of work over which to 

spread it. 

(b) JOB OVERHEAD 

Job Overhead is made up of pay- 




Form costs are made up of material 
and bench labor ; labor removing and 
re-erecting; carpenter work reshaping 
and repairing form units. Well-built 
units are a sound economy, because 
they can be re-used oftener, and with 
lower handling and repair costs. A 
form set costing $2200 may provide 
only 3 or 4 uses, at a prorated cost of 
say $600 per floor; while a similar set 
of forms, built for 6 or 8 uses, may cost 
but $2500, and give a per-floor cost of 
$350. In addition, handling and repair 
costs are usually less for the well- 
built set. 



9 



roll charges and expenses, including superin- 
tendent, timekeeper and watchman; it aver- 



2. FORM COSTS: 

Form Costs are made up of material and 



ages between 320 and £30 a day. In some lo- j a |^ or re quired to build forms; labor removing 
calities, various foremen and skilled workers an( j re _ ere cting forms; carpenter work reshap- 



are 



also carried on straight time; this may j n g and repairing form units. 



mean as much as 365 a day or more. 



Forms are made for just one purpose, to 



So, job overhead ranges from 330 to 3100 a ^old "wet" concrete— that is, to act as a mold 
day, on buildings of moderate size. In addi- unt jj t j ie con crete hardens sufficiently to re- 
tion, there are job-office and other charges, ta j n | ts s hape. Hence, the investment in forms 



including liability. 

These costs run on for the duration of the 
job; the sooner the work is completed, the 
lower the job overhead charges against it. 



(c) EQUIPMENT COSTS: 

Equipment Cost* ire a daily charge against 



is productive only during the first few hour 
after concrete is placed. 

Ideally, therefore, forms should be removed 
the next morning after concreting; the nearer 
this ideal is approached in practice, the larger 
the profit earned by an investment in forms. 

But early form removal depends upon the 



the job, whether the contractor owns the kind and amount of cement used, which brings 

equipment <>r rents it. If concrete is placed U8 t0 tJlc third t()sr f actor — total cement cost. 

,v w inste i of every other week, the 

pro rata equipment cost in a cubic yard of 

oncrete is cut in hall. _^_^^^___ 



TOTAL TIME COSTS: 

Here. then, re tin kinds of OVeitu -I 

t the total ol which depends upon the 

time it tak to lish :i job. Il ill these t 

are i ui I (and the contract* paj - them, 
wheth h< figui them or not . th trer- 

kI ,, r ti i« Hj exceed da) 

e\ n on a II I > moderate-sin jol 

tlu\ run h m I to KM and on larj. r 
jol prop- tion. 

It th *tfl amount to onl) £50 a da\ 

in l it t working days \ mrct 

then <>\ eil id or time bar; 
,w. the b imount t 3 If sound 

planning m climin.it' 2^ da >e are 

redu( 1 1^ £14* • 



Both time and form costs are minimized if forms 
are removed the first morning after concrete is 
placed. But early form removal depends upon the 
type and quantity of cement used. Which intro- 
lu« s a third factor — total cement cost. So the 
problem of finding the cheapest erection sched- 
ule comes down to this: what kind of tonerete 
will produce the lowest overall tost, taking all 
three cost factors— tinv forms and cement — 
into consideration. 






3. CEMENT COST: 

Cement Cost depends upon how much 
cement is used in the mix, and upon the type 
of cement selected. With a small amount of 



provide the required workability. 

Then, there are the two types of cement: 
Lone Star Cement, which gains strength at a 
moderate rate, and Tncor' 24-Hour Cement, 



water, say 5 gal. per bag of cement, the concrete which produces high strength at early periods 
has high strength, particularly at early periods, but has a higher first cost than Lone Star. 



but over 7 bags of cement per cu. yd. are 
needed to produce the desired workability. On 
the other hand, with 8 gal. of water per bag of 
cement, early strengths will be low, but only 



So the problem comes down to this: 
What kind of concrete will produce the 
lowest overall cost of Time, Forms and 



5 bags of cement per cu. yd. are needed to Cement? 




11 



AGE STRENGTH CURVES FOR LONE 




6000 



I *INCOR'-24 HOUR CEMENT 



2 1 5000 






: 4000 



3000 






^ 2000 



V 




1000 



E 

o 







. 



Tests of tuic-in. cy 
according A.S.T.M- Specifications; 
Cured Moist at 70*F. 



1 I 3 4 5 6 7 10 14 Z\ 28 

Aqe of Concrete, Days - log scale. 
FIGURE 1: 



6000 



^ 5000 



; 4000 



3000 



c 



2000 



V 






000 







LONE STAR PORTLAND CEMENT 



Tests of 6a 12- in cylinders, r-adc 

according A. ST M. Specifica tions; 
Cured Moist at 70°F. 




I 2 3 4 5 67 10 14 21 26 

Age of Concrete, Days - log. scale. 

FIGURE 2: 



How the AmonDt ol Water Affect* Concrete Strength at Ages up to 28 Day., for both Lone Star and 'Incor' Cement*. 



To find the relation between strength and quantity of 
mixing water at any age, enter either Lone Star or 
'Incor* diagram with two known factors and find the 
third or unknown value, thus: 

(1) Find the water content that results in 2000 lb. con- 
crete at 2 days. Using 'Incor,' start at 2000 lb. at the left 
and move towards the right until the 2 day vertical line 
is reached. The 8 gal. inclined line passes close to this 
point so use 8 gal. per sack of cement. With Lone Star, 



the 2000 lb. and the 2 day lines intersect midway be- 
tween the 5 gal. and the 6 gal. inclined lines. Use 5!6 

gallons. 

(2) When will 6 gal. concrete develop 2000 lb? Enter 
the Lone Star diagram at the left and move upwards 
towards the right midway between the 6 gal. and 7 gal. 
lines until the horizontal 2000 lb. line is reached at 4 
days. In like manner, it is found that 2000 lb. is obtained 
with ' Incor' in one day. 













9 




FIGURE 3: 

How the Amount of Water and Cement 

Affect* Workability* 

To find the relation between cement, 
water and slump, enter the diagram 
with two known properties and find 
the third or unknown thus: 

(1) Given a 3 slump, b'j gal. of 
water per sack of cement, find the ce 
ment content. Move right on 3 
slump line till 6'i gal. line is reached 
and read 5 bags of cement per cubic 
yard at bottom of diagram. 

(2) Given a 5 slump, frM bags of 
cement per cubic yard, find water 
content Move right on 5" slump 
line until 6*2 bag vertical line is 
reached; 5! 2 gal. line crosses at this 
point. 

(J) Given a 5.5 bag concrete, 6M gal. 
of water (6^ gal. is midway between 
the 7 gal. and 6' 2 gal. lines). Find the 
slump. Move upward along 5.5 bag 

6'2 gal. 



Cement Content - Bags per cu. yd. Concrete. 



line until midway bet 

and 7 gal. line — result 6 slump. 





12 




the Low-Cost Schedule 




i 



METHOD for finding the lowest overall It will also be noted that daily time costs, 

cost of time, forms and cement is outlined form assembly and concreting time are fixed by 

below, using as an example a typical concrete job conditions; but the length of the strength- 
gaining period can be increased or decreased, 
depending upon the amount and the type of 
cement used. Since the forming and concreting 
periods are inflexible, the time required to erect 
the frame will increase or decrease as the 
strength-gaining period becomes longer or 
shorter. A shorter strength-gaining period de- 
creases the time cost but also increases the 
cement cost; so again we have the question, 
what cement cost will produce the lowest total 
cost of time, forms and cement? 

First, Find the Cement Cost: Cement cost var- 
ies with the kind and the quantity of cement 
used. But both kind and quantity depend upon 
how soon the required strength of 2000 lb. per 
square inch is developed. 

The strength of the concrete is also afTected 
by the quantity of water used; as the water 
increases, the strength decreases. So it is nec- 
essary first to find how much water should be 
used in order to obtain 2000 lb. concrete at 
periods ranging from one to seven days. 

Figure 1 shows that with 'Incor' 24-Hour 
Cement, 2000 lb. strength is secured at one day 
with 6^ gal. of water per bag of cement, and 

■ 

at less than two days with 7 l /2 gal. (the max- 
imum permitted by this specification). 

Figure 2 shows that Lone Star develops 2000 



frame structure, as per following job data: 

Plan: 80' X 125'= 10,000 sq. ft. 

Height: 6 stories and roof = 7 floors. 

Superstructure Concrete: 1400 cu. yd. 

Design of Concrete: Not more than l)/z gal. 
of water per bag of cement nor less 
than 5 bags of cement per cubic yard 
of concrete. 

Form Removal: After concrete has a com- 
pressive strength of 2000 lb. per sq. in. 

Time Cost: Fixed and job overhead plus 
equipment charges, #100 per day. 

Cement Cost: Lone Star Cement, $2.00 per 
bbl. 'Incor' 24-Hour Cement, 32.50 per 



bbl. 

Cost of Forms: One floor of forms. 
Two floors of shores . 



Cost one form set 



Two floors of forms 



floors of shores 



Cost two form sets 




$2500 
1200 

#3700 

#5000 
2100 

#7100 



Construction Schedule: 5 day work week. 
For each floor: 6 days to strip and re- 
assemble forms, place steel and set con- 
duits. 1 day to pour concrete. Form re- 
moval based on concrete strength. 

This is not a "rush" job, so the number of days 
required to erect the frame is up to the con- 
tractor. Form costs are given for both one and 
two form sets; per-barrel cement costs are 
shown; but the kind of concrete, and hence the lb. at 3 days using 6 gal., 4 days with 6% gal., 
total cement cost, can be varied. 

13 



5 days with 6% gal., 6 days with 7 gal,, and 





Table III 






Days for 

2000 lb. 

per aq. In 


Kind of 

Cement 


Gals, of 
Water per 

Bag of i 

Cement 


Cement 

Bafts per 

cu. yd. 


Cement 
per cu. yd. 


Cement 

Cost 
for 1400 

cu. yd. 


1 


'Incor' 


6'/2 


5.6 


$3.50 


$4900 


2 


'Incor' 


TA 


5.0 


3.13 


4382 


3 


Lone Star 


' 


6.2 


3.10 


4340 


* 


Lone Star 


6'/i | 5.6 


2.80 


3920 


5 


Lone Star 


614 


5.4 


2.70 


3780 


■ — 

6 


Lone Star 


7 


5.2 


2.60 


3640 


7 


Lone Star 


m 


5.0 


2.50 


3500 



7 days with 7}^ gal. These water contents are 
entered in Table III, Column 3. 

This fixes the amount of water per bag of 
cement, but the amount of cement in each case 
will depend upon the desired concrete worka- 
bility. Let us assume that a 6-inch slump con- 
crete will have the proper workability for this 
job, and determine from Figure 3 the number 
of bags of cement which should be used with 
each water content. 

Using 6J/2 gal. water and 6-inch slump, 5.6 
bags of cement per cubic yard are needed; l x /i 
gal., 4.9 bags. But the minimum cement con- 



cement price per barrel and the resulting ce- 
ment costs per cubic yard are recorded in 
Column 5. 

There are 1400 cubic yards of concrete in the 
building, so each cement cost for one cubic 
yard as given in Column 5 is multiplied by 
1400 to obtain the corresponding total cement 
cost shown in Column 6. 

Second, Calculate Time Cost: Next step is to 
ascertain the effect of these seven strength- 
gaining periods on the total time required to 
erect the building frame. Table I (page 7) 
shows that for 6-day forming and one day form 
removal, 49 days are needed to complete seven 
floors; 2-day form removal, 52 days. The re- 
maining erection times are similarly deter- 
mined and entered in Table IV. Then, on the 
line below erection time, is recorded the corre- 
sponding time cost at 3100 per day. 

Third, Form and Cement Costs: Form costs as 
shown by job data on page 13, are then en- 
tered in Table IV. And, finally, cement costs, 
as given in Table III, Column 6, are entered. 



tent specified is 5 bags, so this figure is entered Using Two Form Sets: Here, the same pro- 



in Table III, Column 4. In the same way, ce- 
ment quantities corresponding to the remaining 



cedure is followed: In Table I, we find that 
frame erection with two form sets requires 49 



watei ontents are ascertained and recorded in days, which is 34900 in time costs. Two form 



Table III. Cement quantities per cubic yard 



sets cost 37100. As forms need not be removed 



show n in Column 4 are then multiplied by the for 10 days, the minimum cement content of 5 









Table IV 
















One Form Set 








Two Form 
Sets 


Form Removal — Days 


1 


2 


3 


4 


5 


6 


7 


9 


1 Erection Time— Days 


49 


52 


57 


67 


67 


67 


73 


49 


I Tim* t 


$ 4,9*0 


$ 5,200 


$ 5.700 


$ o,700 


$ 6,700 


$ 6,700 


$ 7,300 


$ 4,9** 


1 Form Cost 


3,700 


3,700 


3,7** 


3,700 


3,700 


3,700 


3,700 


7,1*0 


Cement < loet 


4.9*0 


4.382 


4,340 


3,920 


3,780 


3,640 


3,5** 


Ji JtW 


Total 


1 $13,5*0 


$13,282 


| $13,740 1 $14,32* 


$14,180 


$14,040 


$14,5*0 


$15,5*0 



14 



1 


Table V 






Lone Star 


'Incor' 


Form Removal - 


—Days 


5 


1 


Erection Time- 




67 


49 


Time Cost . . 
Form Cost . 1 




$6,700 


$4,900 




3,700 


3,700 




Cement Cost . 




3,780 


4,725 1 




I Total 




$14,180 


$13,325 




1 



bags of Lone Star per cubic yard will suffice. 
This results in a cement cost of 33500. 

Finally, Compare Overall Costs: Adding up the 
eight columns in Table IV, we find that 
the total cost of time, forms and cement de- 
creases as the time of erection is shortened. 
The two 'Incor' schedules have a lower cost 
than any of the Lone Star schedules, proving 
that money is saved by eliminating needless 
time in the strength-gaining period. Of course, 
as the value of time is increased or decreased, 
other schedules may be more economical. 
Thus, in this instance, if time costs more than 
^180 a day, the erection schedule with one-day 
form removal becomes cheapest. On the other 
hand, if time is worth only #45 a day, the 6-day 
form-removal schedule is cheapest. Similarly, 



cubic yard, (the usual 1—2—4 mix); all other 
conditions being the same as in the previous 
example. With cement content fixed, it is neces- 
sary to find the amount of water per bag of ce- 
ment that will produce a 6-inch slump concrete; 
and then determine the effect upon the strength- 
gaining period and upon total time costs. 

From Figure 3 we find that a 5.4 bag mix 
requires 6% gal. of water per bag of cement 
for a 6-inch slump; from Figure 1, that a 6^4 
gal. 'Incor' concrete will develop 1950 lb. in 24 
hours; and from Figure 2, that a similar Lone 
Star concrete will develop 2000 II). within 
5 days. 

Table I shows that 49 days are needed to 
erect the building frame using 'Incor', and 67 
days with L>ne Star. Time, form and cement 

costs are entered in Table V. A comparison of 

cosi as mown in this Table, indicates that 
under the given conditions 'Incor 1 again shows 

an overall living, in this case, $855. Compari- 
son with I able IV indi ttes that the cost of a 
second form set is higher than cither the Lone 

Star or 'Incor' schedules. 

Here again it is seen that the er< tion sched- 



any set of conditions can readily be reduced to u l e making the best use of time resull in the 
a simple comparison indicating which erection lowest erection est. 
schedule shows the lowest overall cost of time, 



forms and cement. 

WHEN MIX IS SPECIFIED 

The foregoing example assumes a specification 
permitting the design of the concrete mix. s< 
that maximum economy can be secured in both 
time and cement costs. Frequently, however. 
it is not possible to design the concrete, because 
proportions are already fixed by specification. 

Take a job where a mix is specified which 



The principles involved in this and the pre- 
ding example apply to all types of concrete 
buildings, large and small; although cost re- 
lationships will of course vary with job ion- 
ditions. With this method, it is easily p< ,ible 
to find out in ad\ nee the most economical 
erection ludul as illustrated by the typical 
dc ribed on the following pages. 

This method points the way t increased 
profits b\ reducing ( : and that i- the pri- 



establishes the cement content at 5.4 bags per mary object of every sound business enterprix 



15 



Six Typical Jobs 



SHOW NET SAVINGS OF 38<? TO $1.49 A CL. YD. OF CONCRETE 




OW this cost-comparison method has 
worked out in practice is illustrated by- 
six buildings recently constructed in different 
parts of the country. These jobs include indus- 
trial, busine , institutional and apartment 
structures — of concrete frame, steel frame and 
wall-bearing construction. Facts were supplied 
by the contractors, and are used with their 
permission. 

1 Hospital Building, State Hospital No. 1, 

Fulton, Mo.— B. D. Simons, Contractor 

Concrete skeleton frame; 5 floors and roof; simple 
rectangular plan . . . 1070 cu. yd. superstructure 



concrete. 



Form Removal: Specified, 10 days using Lone Star 
Cement, 3 days using 'Incor.' 

Form Cost - ; 7a set. 

Time Cost: $28.50 per day for job overhead. 



Construction Schedule: 6-day work week; 5 days to 
strip and re-assemble forms, place steel and set 
conduits; one day to pour concrete. 

Mr. Simons figured the job for 10-day form 
removal, w ith both one and two form sets, and 
for 3-dav form removal, using 'Incor' with one 
form set. As a result, he used 'Incor* and one 
form set for all superstructure concrete, saving 
30 days, and enabling him to get the frame up 
before heavy winter weather set in. 



COMPARATIV E COST SUMMARY 

lO-Dav Form Removal 



Cost Factors 



Total Erection Time 
Time Cost (a $1 90 
Forms (a 3937 a set 
Cemenr Cost 



Da\ 



Totals 



th One 
Form Set 



78 
S2223 
937 
3120 



S6280 



With Two 
Form Sets 



41 
SI 169 
1874 

120 



K 163 



3-Day Form 

Removal 

With One 

Form Set 



48 
SI 368 
'37 






'Incor' saved $578, or 54f a cu. yd. 




16 




2 Royal York Apartments, Columbus, Ohio 

Nelson-Pedley Co., General Contractor 
R. L. Wirtz, Concrete and Brick Cont/actor 

Concrete skeleton frame; 6 floors, roof and pent- 
house; "U" shaped plan, around three sides of 
court . . . 2000 cu. yd. superstructure concrete. 

Form Removal: 7 days using Lone Star Cement, 
1 day using 'Incor'. 

Form Cost: 2 floors of forms, 3 sets of shores— #7000; 
with 'Incor', 1 floor of forms, 2 sets of shores — 

34200. 

Time Cost: $46.50 per day, sub-contractor's over- 
head only. 

Construction Schedule: 7-day week; 7 days to strip 
and re-assemble forms, place steel and set conduits. 

Mr. Wirtz figured the job three wa\ — 7-day 
form removal, first with one form set, then 
with two form sets; and one-day form removal 
using 'Incor' and one form set. One-day form 



removal \sith 'Incor' and one form set cost 
3900 less than the next cheapest Si hedule. 

By working 7 days a ueek and pouring i 
floor a week, Mr. Wirtz got the job enclosed 
before heavy weather set in, saving heating 
expense on both concrete and brick work 
He advanced erection time by 1 ' •> months, 
the value of that time to the owner bein 
310,500; he aK ed the general i n tractor 

6 week overhead. 



COMPARATI\ 1 COST SUMMARY 


( 


7 -Day Form Removal 


l-Day m 
Removal 

form i i 


With r 

Form -"• 


With 1*., 

F'jrm 


1 otal Erection lime— Da 
lime • i 50 
Forms 
Cement vOsr 


100 

♦200 

* 


• 

00 

4200 


2700 

4200 

5250 


Totals 




$\ -JO 


X12.150 



'Incor' saved $900, or 45* a cu. yd. 



17 






3 Popham Hall Apartments, Scarsdale, N. Y. tional forms valued at #3000 were considered, 

Willcox Construction Co., Contractor ^ ^ ^ necessity Q f leaving the forms Oil 

Concrete skeleton frame; 6 floors, roof and penthouse; certain long-span sections in place longer than 

2270 cu. yd. superstructure concrete. 3 days He a j SQ fi gurec J tne job with 'Incor' 

Form Removal: Permitted in 3 days, using Lone Star; ano j one-day form removal. The 'Incor' sched- 
1 day using 'Incor'. u | e p rove( j to De both faster and cheaper, en- 
Form Cost: £6000 with incor'-, #9000 with Lone Star. abling the contractor to promote the owner's 



Time Cost :$\(> 7 a day for general overhead, job over- 
head and equipment charges. 

Construction Schedule: 5-day week; 4 days to strip 
and re-assemble forms, place steel and conduits; 
one day to pour concrete. 



On this job, the contractor was working against 
time; the apartment house had to be ready tor 
Jctober 1st occupancy. He estimated the job 
using Lone Star with 3-day form removal. In 
order to maintain this schedule, 50% addi- 



interests through earlier completion and lower 
construction costs. Work on the frame began 
June 15; roof was poured on August 3rd. 



COMPARATIVE 


COST SUMMARY 


Cost Factors 


1-Day Form 

Rcmovil 
with Lone Star 


1-Day Form 

Removal 
with 'Incur' 


Total Erection Time— Days . 

lime Cost ( ^167 


• • 


4S 

#75 1 5 
9000 
( S60 


38 

#6346 
6000 
7440 




Cement Cost 




$23,075 


$19,786 





Incor' saved $3289, or $1.45 a cu. yd. 











The same kind of savings are possible on wall- 
bearing jobs, except where it takes longer to 
run up brick work than it does to cure concrete , 
strip and re-assemble forms. A typical wall- 
bearing job follows: 



4 Psychiatric Clinic Building, State Hospital 

No. 1, Fulton, Mo — B. D. Simons, Contractor 

Brick-bearing walls; 3 floors and roof, resembling a 
spread "U fl in plan; 2160 cu. yd. superstructure 
concrete. 

Form Removal: Specified, 10 days using Lone Star 
Cement, 3 days using *Incor\ 

Form Cost: $1540. 

Time Cost: $37.75 per day for job overhead. 

Construction Schedule: 6-dav work week; each floor 

■ 

formed and poured in 3 sections; atter pouring a 
section, brick work was run up to next floor; on 



each se^ tion f 5 da quired to strip and n ru- 
ble forms, place steel and set conduits, da) to 
pour concrete. 

On this job, Mr. imons, who was also the 
contractoi n the State Hospital job previously 

mentioned, compared the cost ol 10-day form 
removal against 3-day torm removal with 
4 Incor\ form c were the same in both cat 

The following cost comparison shows that in 
this instance 'Incur' and 3-day form removal 
was the Iowh t schedule: 



1 COMPARATIVE COST SUMMARY 


• 


Rem A 


J Ojv Form 

novaJ 


1 tai Ercc 'Tin 1 > * 

lime ' sr ( , Day 

Forms 

Cement Co«t 


i i 

21 


49 

£1 
1 10 

IS 




J 11.041 


3510,215 





'Incur' saved $826, or 38< a cu. yd. 



19 







Substantial savings are also obtained in steel- 
frame structures, as indicated by the following 
examples: 

5 Coca Cola Bottling Works, Washington* D.C. 

Davis & Piatt, General Contractor 
E. W. Kryz, Concrete Contractor 

Steel-frame plant addition; 2 floors and roof; 700 cu. 
yd. concrete in floor slabs and fire-proohng. 

Form Removal: Permitted in 7 days using Lone Star 
Cement; 1 day using Tncor\ 

Form Cost: 3900 per set. 

Time Cost: $32.50 per day for job overhead and 
equipment charges. 

This was a rush job, the additional space being 
needed in order to expand mid-summer pro- 



duction of bottled Coca Cola. Mr. Kryz esti- 
mated three concreting schedules; 7-day form 
removal and one form set took too long; Tncor' 
with one form set and 1-day form removal was 
cheaper than 7-day form removal with two 
form sets, and that is the way the job was built. 



COMPARATIVE COST SUMMARY 


Cott Facrors 


7-Dav Pom 

Removal 

W.rh Two 
Form Ser I 


i-Day Form 

Removal 

With One 

Form Set 


Total Erection Time— Days ... 
Time Cost @ £32.50 a Day . . . . 


15 

1800 
2100 


IS 

$ l 

900 
2625 


Cement Cost 


Totals .... 


£» 


94,013 



'Incor' saved $375, or 53? a cu. yd. 



In cold weather, early service strength has 
added value, as illustrated by the following job: 

6 New England Power Co. Bldg.. Boston, Mass. 

T. A. Pearson Associates, General Contractor 
Scully Company, Concrete Contractor 

Steel frame; 11 stories and root 3120 cu. yd. super- 
structure concrete. 

Heat Protection : 3 days using Lone Star; 2 days using 
Tncor' 24-Hour Cement. 

Form Cost: $2500 per set. 

Heat-Protection Cost: Fuel, £33. 60 per day; labor 
tending hres, £34.10 per day; total. £67.70 per day. 

Time Cost: £162 per day overhead. 



Construction schedule: 5-day week; concrete placed 
3 days a week, half a floor at a time; \ l /i floors a 
week; 6 days to strip and re-assemble each form 
set, place steel and set conduits; one day to each 
pour. 

On this job, the Scully Company figured two 
erection schedules; 3-day heat curing and four 
form sets, against 2-day heat curing with 
Tncor' and three form sets. The Tncor' sched- 
ule was used, and resulted in a net saving 

of 34654. or £1.49 a cu. yd. of concrete. 

Concrete work started December I5th, was 
finished before February' 1st — better than \\A 



20 



floors a week; concrete was run only two floors ditions. A clear-cut example of the all-around 



behind riveting gangs all the way up the build- 
ing. Finishing operations were quickly and 
easily performed, despite adverse weather con- 



COMPARATIVE COST SUMMARY 


Cost Factors 


1-Day Heat 

Curing With 

4 Form Sets' 


2-Day Heat 

Curing With 

3 Form Sets 


Total Erection Time— Davs ... 

Time Cost (a £162 

Forms 


47 

£76 1 4 

10,000 

4874 

7600 


32 
555184 

7500 
3250 
9500 


Heat Protection 


Cement Cost . 


1 Totals . . 


830,088 


£25.434 



advantages of scheduling a job to make the 
best use of time. 



'Incor' saved $4654, or $1.49 a cu. yd. 



Here, then, are six building jobs, fairly repre- 
sentative of the various types of concrete con- 
struction, each showingthe practical advantages 
of estimating in advance the erection schedule 
which produces the lowest overall cost of time, 
forms and cement. Net savings ranging from 
38^ to $1.49 a cu. yd. of concrete suggest that 
this method is well worth considering. 




21 



j| 



Notes 



on 



Job 



Plannin 





N order to get the lowest form cost per floor require extensive repairs after removal and be- 



or per cubic yard of concrete, the most 



fore re-use, have a lower first cost but are 



should be made of every opportunity for form expensive in the end. Sturdy, well-made units, 
re-use. Many buildings do not have typical designed to strip without damage and with- 
floors all the way up, but duplication of plan stand rough handling, are a good investment, 
usually occurs in certain floors or 
parts of floors. Hotels and apart- 
ment houses, for example, have 
several lower floors cut up by lob- 
bies, dining, service and meeting 
rooms, but the upper floors are 
usually typical. 

Then there are buildings with 
typical wings where forms can be re- 
used by staggered construction or 



by moving forms horizontally. In 

this way, forms can often be re-used 

n broad, low buildings which are 

ymmetrical about the center line. 

WELL-BUILT FORMS PAY 

Even in non-typical buildings. 

there are instances where forms can 

be designed so as to make possible 

frequent re-use; in such cases, stand- 
trd form units can be made of such 
M/es that various combinations of 

units will meet practically any di- 
mension in a building. Such a solu- 
tion calls for ingenuity and carefully 
regulated job procedure, but the 
s vings are usually well worth the 
effort. 

Flimsy form units or those which 




Well -designed concrete made with Lone Star or 'Incor' 
holds together and places easily with minimum separa- 
tion, producing dense, uniform concrete. Both Lone Star 
and 'Incor' produce concrete of the same high strength 
and durability. While 'Incor' hardens rapidly, it too 
allows ample time for mixing, placing and finishing. 



22 



Thus, a set of forms costing 32200 may pro- 
vide only 3 or 4 uses, at a prorated cost of, say, 
3600 per floor; while a similar form set, good 
for 6 or 8 uses, may cost but 32500, or a per- 
floor cost of 3350. In addition, handling and 
repair costs are usually lower for the well 
built set. 

The kind of building and the surface finish 
required in effect determines the number of re- 
uses that can be obtained without excessive 
rebuilding. In an apartment house, for exam- 
ple, if ceilings are to be plastered, a rough sur- 
face finish is permissible, and forms can be 
re-used oftener than in a similar structure 
where ceilings are to be painted directly on 
the concrete. 

BUILDING "MAKE-READY" 

It also pays to consider the most efficient meth- 
od of scheduling the "make-ready" operations 

that is, the work which has to be done before 
concrete can be poured. Sometimes, as in a 
warehouse, it is merely a case of erecting sim- 
ple forms and placing re-inforcement. Again 
as in hotels, hospitals or apartment buildings, 
with a lot of equipment, inserts, wiring and 
plumbing to be accurately set, more time is 
required. 

Here, too, the element of time or overhead 
expense enters. It may, for example, pay to put 



FIGURE 4: 

These two charts illustrate a simple way of determining the 
time required to erect a building frame, knowing the number 
of days needed on each floor to (1) strip and re-erect forms, 
(2) place concrete, (3) permit concrete to gain service strength* 

This method was followed in preparing Tables I and II, page 
7. Note that the total number of working days in the sched- 
ules are the elapsed time minus week-end days on which no 
work was done. Also note that total working days agree with 
those given in Table I for the same conditions. 



1 SCHEDULE No. 1 CEMENT LONE STAR 






Forms — Stripping, Assembly, Steel Setting 6 days 

Forms — Removal after Concrete Placed 6 days 


Mon 


Tue 


Wed 


Thu 


Frl 


Sat 


Sun 


1 S 


2 S 


3 S 


4 S 


5 S 


6 


7 


8 s 


9 P, 


,o C 


"C 


,2 C 


13 c 


,4 C 


,5 S 


16 s 


,7 g 


18 s 


19 s 


20 


21 


22 s 


23 p 2 


24 c 


25 G 


26 c 


27 c 


28 C 


29 s 


30 s 


31 g 


32 s 


33 s 


34 


35 


3* S 


37 p, 


38 C 


39 c 


40 c 


4. G 


42 G 


43 s 


44 s 


45 s 


« s 


47 s 


48 


49 


50 s 


5 p 4 


52 c 


53 c 


54 C 


55 C 


^C 


57 s 


58 S 


59 s 


60 s 


61 s 


62 


63 


64g 


45 P 5 


44 c 


67 c 


63 C 


49 C 


70 C 


71 s 


72 s 


73 s 


74 g 


75 s 


76 


77 


78 s 


79 p* 


80 C 


81 c 


82 c 


W C 


- 84 C 


85 s 


86 S 


87 s 


88 S 


89 g; 


90 


91 


92 s 


93 P 7 


94 


95 


96 


97 


98 


99 


100 


101 


102 


103 


104 


10S 


106 


107 


108 


109 


110 


111 


112 


113 


114 


115 116 


117 


118 


119 


Working Time .... 67 days Elapsed Time .... 93 days 



SCHEDULE No. 2 CEMENT 'INCOR' 






Forms— Removal after Concrete Placed 1 day 


Mon 


Tue 


Wed | Thu 


Fri 


Sat 


Sun 


1 S 


2 S 


3 S 


4 S 


5 S 


6 


7 


8 S 


9 P, 


10 § 


n s 


12 g 


13 


14 


15 s 


14 s 


,7 S 


18p a 


19 s 


20 


21 


22 S 


23 s 


24 s 


25 s 


24 s 


27 


28 


29 p, 


30 S 


31 g 


32 s 


33 S 


34 


35 


34 S 


37 s 


38 p 4 


39 S 


40 § 


41 


42 


43 S 


44 S 


45 s 


46 s 


47 Ps 


48 


49 


50 S 


51 s 


52 s 


fl S 


M S 


55 


56 


57 s 


58 p 4 


59 s 


40 S 


6, S 


62 


63 


64§ 


65 s 


"S 


47 P 7 


68 


69 


70 


71 


72 


73 


74 


75 


76 


77 


78 
85 


79 


80 


81 


82 


83 


84 


86 


87 


88 


89 


90 


91 


92 


93 


94 


95 


96 


97 


98 


9<? 


100 


101 


102 


103 


104 


105 


106 


107 


108 


109 


no 


111 


112 


113 


,H 


115 


116 


117 


118 


119 


Working Time . . ' . ,49 days El 


apsed Tin 


ie .... 67 days 



s 
p 
c 



Days forms are stripped and re-assembled 

Days concrete is placed 

Days concrete cures— that is, the strength-gaining period 



23 



on more labor to complete form assembly, say, elaborate forms are of course necessary if prog- 
in 4 days instead of 5, in order to save a day's ress of several craftsmen, such as plasterers, 
overhead on each assembly. Example: 



If labor for 5-day assembly costs 3200 a day 
and overhead is 3100 a day, the contractor can 
afford to spend up to 3275 a day for labor to 
complete assembly in 4 days, and still break 
even. Anything less than 3275 a day for labor 
to accomplish 4-day assembly is a clear saving. 

SIMPLE SCHEDULE-FORM USEFUL 

In estimating the lowest cost erection schedule, 
a form similar to that shown in Figure 4 is use- 
ful. By means of symbols for the various opera- 
tions, erection time under any combination of 



bricklayers and plumbers are included. 

CAREFUL PLANNING PAYS 

- 

The importance of thorough planning cannot 
be over-emphasized. Witness the experience of 
the contractors on the typical jobs previously 
outlined herein. By careful advance planning, 
these contractors saved from 38£ to 31-49 per 
cubic yard of concrete, mainly because they 
balanced their outlay for forms and cement 
against the cost of time. In other words, they 
made each unit of time earn the maximum 
return. That is the essence of the problem of 



conditions may readily be calculated. More cutting concrete costs. 




Decide 



OR every building project, there is 
an erection schedule which shows 
the lowest overall cost of time, forms 
and cement. Money can usually be saved 
by figuring the lowest -cost schedule, 
using the quick, easy method outlined 
in this book. 

In some cases, faster schedules are 
cheaper; in others, the reverse is true. 
Which means that on some jobs 'Incor'* 
24-Hour Cement, which is self-support- 
ing in one-fifth the usual time, provides 
maximum economies; on other jobs, 
Lone Star Cement is the better buy. 

It pays to estimate each job carefully 
in advance. Then, let economy decide 
which of these two cements to use. You 
gain either way, because— Better Cement 



Makes Better Concrete. 



'Reg. U. S. Pat. Off. 






*K? 






Printed in U. S. A 




[BLANK PAGE] 








INTFRNATIONAI